The invention relates generally to duct tapes and more particularly to duct tapes which have an adhesive which does not leave an adhesive residue upon removal.
Duct tape is routinely employed by musicians and stage technicians to affix cables, wires lights, and other appliances usually in anticipation that the attachment is temporary, and will have to be removed or repositioned in the future, where the duration of attachment can vary from a few hours to years. Duct tape is the preferred type of pressure sensitive tape because it is relatively inexpensive, it has a tensile on the order of several pounds per inch, and yet in contrast to filament reinforced or filmic tapes which have to be cut, duct tape has a cloth backing, usually a scrim, that can be easily torn by hand. Duct tape is configured such that the adhesive is of sufficient mass and tack that it adheres well to most surfaces, including vinyl flooring, carpeting, concrete, wood, brick, metal, polymeric veneers, glass and polyolefins such as pvc and polyethylene. In order to stick to these wide variety of substrates, the adhesive is usually based on natural rubber that is tackified to a point where it is quite soft. The preferred process for coating is calendering, because a substantially heavy coat weight has to be applied to coat over the relatively coarse cloth. Also, many of the substrates, such as concrete and carpeting, have rough surfaces that require a lot of adhesive to affect good adhesion. The cloth is usually a scrim, that is frequently laminated to a thin inexpensive film of low density polyethylene. A common problem associated with duct tape is that upon removal it leaves an adhesive residue, which depending on the substrate is usually difficult, at best, to clean. Very often the residue problem is exacerbated along the interfacial edge of the tape and the underlying substrate, as a consequence of oxidation of the adhesive. The instant invention is an article of manufacture and a process for making the same, wherein the article is a type of duct tape with a very aggressive, yet non-depositing adhesive, wherein the adhesive has excellent cohesion as well as adhesion, and the process for making the duct tape is one wherein the adhesive is coated as a 100% solids extruded molten material.
The prior art on duct tape is largely devoted to discussion on various methods to lower cost, while still maintaining performance. Two examples of this are Adams U.S. Pat. No. 5,108,815 wherein the backing is embossed in order to lower density, and DeCoste U.S. Pat. No. 4,740,416 wherein microspheres are dispersed in a polymeric matrix layer in order to achieve a lower density.
Don Satas in the Handbook Of Pressure-Sensitive Adhesive Technology discusses duct tapes briefly, and suggests that a duct tape could be prepared using a hot melt extrusion coating process. An adhesive formula, based on the rubber Kraton D-1107, which is a Shell Chemical Company tradename for a block copolymer rubber based on styrene and isoprene, is recited as potential formulation.
The prior art literature largely does not address the topic of duct tapes that do not leave an adhesive residue upon removal, probably because many applications for which duct tape are intended are substantially permanent.